In an injection molding apparatus having a plurality of valve-pin gated hot runner nozzles for injecting melt into a plurality of mold cavities, proper alignment between the moving components is critical in order to maximize the lifetime of the components and produce high quality molded parts.
Typically, prior art valve-gated nozzles include reciprocating valve pins, which retract to open the mold gates and extend to close the mold gates. In this type of arrangement, the valve pin is typically un-guided during the opening and closing phases of the injection cycle. As such, each valve pin must re-align itself every time it engages the mold gate. This can cause both the valve pin and the mold gate to experience wear. Thus necessitating frequent replacement of these parts, which can be costly.
Several prior art valve-gated nozzles include continuously guided valve pins, which reduce wear on the valve pin and mold gate. These prior art nozzles are typically limited to molding articles having a hole, such as a compact disc, for example. U.S. Pat. No. 5,423,672 to Gordon discloses a valve-gated nozzle for molding products having a hole.
A further disadvantage of prior art valve-gated nozzles is that the size of the piston may limit the number of applications for the nozzle. For example, nozzles having large pistons may not be used in an injection molding apparatus requiring a small pitch between the nozzles.
It is therefore an object of the present invention to obviate or mitigate at least one of the above-noted disadvantages.